Show simple item record

dc.contributor.advisor Finkelstein, Gleb en_US
dc.contributor.author Mebrahtu, Henok Tesfamariam en_US
dc.date.accessioned 2012-05-25T20:13:52Z
dc.date.issued 2012 en_US
dc.identifier.uri http://hdl.handle.net/10161/5487
dc.description Dissertation en_US
dc.description.abstract <p>The role of the surroundings, or <italic> environment </italic>, is essential in understanding funda- mental quantum-mechanical concepts, such as quantum measurement and quantum entanglement. It is thought that a dissipative environment may be responsible for certain types of quantum (i.e. zero-temperature) phase transitions. We observe such a quantum phase transition in a very basic system: a resonant level coupled to a dissipative environment. Specifically, the resonant level is formed by a quantized state in a carbon nanotube, and the dissipative environment is realized in resistive leads; and we study the shape of the resonant peak by measuring the nanotube electronic conductance.</p><p>In sequential tunneling regime, we find the height of the single-electron conductance peaks increases as the temperature is lowered, although it scales more weakly than the conventional T<super>-1</super>. Moreover, the observed scaling signals a close connec- tion between fluctuations that influence tunneling phenomenon and macroscopic models of the electromagnetic environment.</p><p>In the resonant tunneling regime (temperature smaller than the intrinsic level width), we characterize the resonant conductance peak, with the expectation that the width and height of the resonant peak, both dependent on the tunneling rate, will be suppressed. The observed behavior crucially depends on the ratio of the coupling between the resonant level and the two contacts. In asymmetric barriers the peak width approaches saturation, while the peak height starts to decrease.</p><p>Overall, the peak height shows a non-monotonic temperature dependence. In sym- metric barriers case, the peak width shrinks and we find a regime where the unitary conductance limit is reached in the incoherent resonant tunneling. We interpret this behavior as a manifestation of a quantum phase transition.</p><p>Finally, our setup emulates tunneling in a Luttinger liquid (LL), an interacting one-dimensional electron system, that is distinct from the conventional Fermi liquids formed by electrons in two and three dimensions. Some of the most spectacular properties of LL are revealed in the process of electron tunneling: as a function of the applied bias or temperature the tunneling current demonstrates a non-trivial power-law suppression. Our setup allows us to address many prediction of resonant tunneling in a LL, which have not been experimentally tested yet.</p> en_US
dc.subject Physics en_US
dc.subject Condensed matter physics en_US
dc.subject Nanoscience en_US
dc.subject carbon nanotube en_US
dc.subject dissipation en_US
dc.subject luttinger liquid en_US
dc.subject quantum dot en_US
dc.subject quantum phase transition en_US
dc.subject resonant tunneling en_US
dc.title Electron Transport through Carbon Nanotube Quantum Dots in A Dissipative Environment en_US
dc.type Dissertation en_US
dc.department Physics en_US
duke.embargo.months 24 en_US
duke.embargo.release 2014-05-15

Files in this item

This item appears in the following Collection(s)

Show simple item record